1. Field of the Invention
The present invention generally relates to top cowls for outboard motors and more particularly relates to top cowls that cover engines of outboard motors and molds for forming such top cowls.
2. Description of the Related Art
Outboard motors can be used to propel watercraft. Outboard motors often have an engine disposed within a protective cowling. The protective cowling typically includes a top cowl and a bottom cowl. Air flows through the cowling to the engine. Air inlet openings at the rear of the cowling can provide fluid communication between the engine and ambient air outside of the cowling. The air inlet openings are typically positioned rearwardly because spray splashed up from waves normally does not flow through these air inlet openings when the watercraft moves in the forward direction.
Japanese Patent Publication No. 2002-349257 discloses that top and bottom cowls are coupled with each other by utilizing bottom side hooks and top side hooks. The bottom side hooks are coupled to an opening edge of the bottom cowl. The top side hooks are coupled to an opening edge of the top cowl. These top side hooks and bottom side hooks can releasably couple the top cowl to the bottom cowl.
The top cowl can be made of a nonferrous metal. Japanese Patent Publication No. 2004-299485, for example, discloses a top cowl that is made of a nonferrous metal. Top cowls are often made of reinforced resin. Unfortunately, these top cowls are heavy and non-recyclable. The top cowls made of resin are typically formed by injection molding or sheet molding. To sheet mold a top cowl, a glass-fiber-reinforced thermosetting resin sheet is placed onto a surface of a mold. For a multi-layer top cowl, several sheets can be placed onto the surface of the mold. The resin sheets are then heated while pressure is applied to form a molded article having a uniform thickness. Unfortunately, these top cowls need to have a relatively large minimum thickness to ensure the top cowl is sufficiently rigid to protect the engine. This minimum thickness can result in a relatively heavy top cowl.
Nonferrous metals, such as aluminum, have been used to make top cowls. These top cowls are often formed by a die-casting process. Unfortunately, marks from a sprue or overflow that remains on the exposed surface of a casting article may require additional manufacturing procedures to produce an article having a suitable appearance. This significantly limits the layout of the sprue and overflow to particular locations, thus limiting design flexibility. These design constraints can also lead to excessively thick portions of the cowl that undesirably increase the overall weight of the cowl.